DESCRIPTION: (Verbatim from the Applicant's Abstract) Glial cell line derived neurotrophic factor (GDNF) is a recently identified peptide shown to elicit marked restorative/protective effects in both rodent and primate models of Parkinson's disease. Although the therapeutic effects implicate its clinical use, since GDNF does not cross the BBB the problem of in vivo delivery still remains an issue. Using an ex vivo gene therapy approach, the applicant has shown that astrocytes transduced with a replication defective retroviral vector express recombinant GDNF in culture and following intracerebral transplantation. Preliminary studies described in the proposal demonstrate that GDNF producing astrocytes provide nearly complete protection of both nigral dopaminergic perikarya and their associated striatal fibers, when implanted near the substantia nigra several days prior to a 6-OHDA lesion in the mouse. The proposed studies are designed to further characterize the expression of recombinant GDNF by grafted astrocytes and to investigate potential in vivo mechanisms by which continuous exposure to low amounts of GDNF confers decreased susceptibility of adult nigrostriatal neurons to 6-OHDA induced toxicity. In addition, experiments are proposed to determine whether GDNF delivered via transgenic astrocytes restores function to atrophic neurons previously damaged by 6-OHDA. Using a murine model of PD, the proposed studies are designed to address the following Specific aims 1) to characterize the long-term expression of GDNF by transgenic astrocytes following intracerebral transplantation 2) to investigate the potential role of the glutathione system and phosphatidylinositol 3 kinase (PI3K) regulated signaling events in GDNF mediated neuroprotection in vivo using transgenic astrocytes and 3) to determine whether GDNF producing astrocytes restore dopaminergic function to damaged nigrostriatal neurons following the onset of degeneration induced by 6-OHDA. These aims will be addressed using a combination of molecular, tissue culture, behavioral and neurochemical methods, in a mouse 6-OHDA model of Parkinson's disease.